Description

Magnetic nanoparticles for therapeutic use may be made from ferro- , ferrimagnetic or superparamagnetic materials. Their major advantage is the possibility to manipulate them non-invasively in an organism using an external magnetic field. Nanoparticles based on iron oxides with a spinel structure (magnetite, maghemite) are the most widely used in medical applications.

Magnetic nanoparticles alone are rarely used for treatment purposes. They are usually encapsulated or placed inside bioinert matrices (various organic compounds or polymers, including naturalpolimers ) to reduce the possible toxic effects of the magnetic phase, increase its physico-chemical stability and enable the immobilisation of drugs on the surface of such capsules or matrices. Encapsulation is usually carried out in suspensions of ultradisperse ferro-, ferri- and superparamagnetic particles containing stabilising reagents, so-called “magnetic fluids”.

One of the applications of magnetic nanoparticles in medicine is targeted drug delivery. Its major advantages include the significant reduction of a drug’s toxic effects on healthy organs, the possibility to locate drug-containing magnetic nanoparticles at a given site of the body using a magnetic field, as well as visualisation of such nanoparticles using magnetic resonance imaging. Another important aspect of magnetic nanoparticles is that they can be locally heated by a high-frequency magnetic field to initiate desorption /de-capsulation of drugs or to induce magnetic hyperthermia. Superparamagnetic particles are generally used as a magnetic carrier for targeted drug delivery because they do not aggregate under a magnetic field; however, the intensity of the magnetic effect is thus reduced, which makes it harder to locate the particles close to the target site, especially in a fast bloodstream.

Magnetic nanoparticles coated with biocompatible molecules (dextran, polyvinyl alcohol, phospholipids) coupled with antibodies to specific antigens are used in magnetic separation technology. For example, magnetic particles coupled with specific antibodies bind to red blood cells, bacteria or cancer cells. For cell separation a suspension of magnetic nanoparticles coupled with specific antibodies is added directly to a biological fluid sample. After 10 to 20 minutes of incubation, the test tube is placed in a magnetic separator, where the the desired magnetically labeled cells are retained on the magnet, while the supernatant is removed.